Load tap change monitoring system and method

Abstract

A system and method for remotely monitoring load tap changes on utility-type equipment are disclosed. In one example embodiment, a sensor measures a voltage before a tap change and compares the measured voltage to a voltage after the tap change. From this information, the direction of the tap change and the distance traveled can be determined. The system and method can also include a timer to measure an elapsed time required to complete a particular tap change and use this time information to determine the distance traveled. The direction of the tap change can be determined from a sensor that triggers the timer. The system and method thereby enable efficient and cost-effective remote monitoring of load tap changes and positions.

1. A method for remotely tracking load tap position changes at a power transformer, the method comprising:
 determining a starting position of a load tap changer of the power transformer; 
 sensing a first status change of a load tap changer drive, without using a physical position encoder; 
 initiating a first data reading upon sensing the first status change; 
 sensing a second status change of the drive, without using a physical position encoder; 
 initiating a second data reading upon sensing the second status change; 
 determining a number of tap step changes of the load tap changer drive from the first and second data readings; and 
 determining a new load tap changer position. 
 
   
   
     2. The method of  claim 1 , wherein the step of determining a number of tap step changes of the load tap changer drive from the first and second data readings comprises:
 calculating a difference between the first data reading and the second data reading; and 
 dividing the difference by a per tap step value. 
 
   
   
     3. The method of  claim 2 , wherein the step of determining a new load tap changer position comprises adding to or subtracting from the starting position of the load tap changer, the number of steps moved by the load tap changer. 
   
   
     4. The method of  claim 2 , wherein the first and second data readings are voltage-level readings. 
   
   
     5. The method of  claim 2 , wherein the per tap step value is user configurable. 
   
   
     6. The method of  claim 5 , wherein the per tap step value is about 0.75 volts. 
   
   
     7. The method of  claim 2 , wherein the number of steps moved by the load tap changer is rounded to the nearest integer value. 
   
   
     8. The method of  claim 1 , wherein the first and second data readings are initiated in real time. 
   
   
     9. The method of  claim 1 , wherein the step of sensing a first status change of the load tap changer drive comprises sensing a current flow in a load tap changer drive motor. 
   
   
     10. The method of  claim 9 , wherein the step of sensing a second status change of the drive comprises sensing a cessation of current flow in the load tap changer drive motor. 
   
   
     11. A method for remotely tracking load tap position changes at a power transformer, the method comprising:
 determining a starting position of a load tap changer of the power transformer; 
 initiating a timer upon sensing a first status change in a load tap changer circuit arrangement, wherein sensing the first status change is accomplished without the use of a physical position encoder; 
 stopping the timer upon sensing a second status change in the load tap changer circuit arrangement, wherein sensing the second status change is accomplished without the use of a physical position encoder; 
 determining a number of tap step changes of the load tap changer from an elapsed time measured by the timer; and 
 determining a new load tap changer position based on the number of tap step changes. 
 
   
   
     12. The method of  claim 11 , wherein the step of determining a number of tap step changes of the load tap changer comprises dividing the elapsed time by an average time per tap step change to determine a number of steps traveled. 
   
   
     13. The method of  claim 12 , wherein the average time per tap step change is configurable. 
   
   
     14. The method of  claim 11 , further comprising the step of determining a direction of movement of the load tap changer after determining the number of tap step changes. 
   
   
     15. The method of  claim 14 , wherein the load tap changer circuit arrangement is comprised of at least one of two load tap changer circuits, wherein a first load tap changer circuit is a raise circuit and a second load tap changer circuit is a lower circuit, and wherein the direction of movement of the load tap changer is determined by whether the first or second load tap changer circuit initiates and stops the timer. 
   
   
     16. The method of  claim 11 , wherein the step of determining a new load tap changer position comprises adding to or subtracting from the starting position of a load tap changer, the number of tap step changes of the load tap changer. 
   
   
     17. The method of  claim 11 , wherein the step of sensing a first status change in a load tap changer circuit comprises sensing a current flow in the load tap changer circuit. 
   
   
     18. The method of  claim 17 , wherein the step of sensing a second status change in the load tap changer circuit comprises sensing a cessation of current flow in the load tap changer circuit. 
   
   
     19. A system for remotely tracking load tap changes at a power transformer, the system comprising:
 a sensor operable to sense a status change of a load tap changer drive, without use of a physical position encoder; and 
 a remote terminal unit in electrical communication with the sensor and adapted to initiate a first data reading upon a first status change of the drive, initiate a second data reading upon a second status change of the drive, and determine a change in position of the load tap changer drive from the first and second data readings. 
 
   
   
     20. The system of  claim 19 , wherein the sensor comprises a hardware current status sensor, and wherein the first status change comprises an initiation of current flow in the drive and the second status change comprises a cessation of current flow in the drive. 
   
   
     21. The system of  claim 19 , wherein the remote terminal unit includes a software application. 
   
   
     22. The system of  claim 21 , wherein the remote terminal unit and the software application are adapted to determine a new tap position. 
   
   
     23. The system of  claim 19 , wherein the first and second data readings comprise voltage readings. 
   
   
     24. A system for remotely tracking load tap position changes at a power transformer, the system comprising:
 a first sensor adapted to sense a status change in a first load tap changer circuit arrangement without using a physical position encoder; 
 a second sensor adapted to sense a status change in a second load tap changer circuit arrangement without using a physical position encoder; and 
 a remote terminal unit comprising a timer electrically coupled to the first and second sensors,
 wherein the timer is adapted to measure an elapsed time between subsequent status changes of either the first circuit or the second circuit, and wherein the remote terminal unit is adapted to determine a tap change from the elapsed time. 
 
 
   
   
     25. The system of  claim 24 , wherein the first and second sensors comprise current sensors, and wherein the first status change comprises an initiation of current flow and the second status change comprises a cessation of current flow. 
   
   
     26. The system of  claim 24 , wherein the remote terminal unit further comprises a software application adapted to communicate with the first and second sensors and the timer. 
   
   
     27. The system of  claim 26 , wherein the software application is adapted to determine a new tap position from the determined tap change. 
   
   
     28. A system for remotely tracking load tap position changes at a power transformer, the system comprising:
 means for determining a starting position of a load tap changer of the power transformer; 
 means for sensing a first status change of a load tap changer drive without using a physical position encoder; 
 means for initiating a first data reading upon sensing the first status change; 
 means for sensing a second status change of the drive without using a physical position encoder; 
 means for initiating a second data reading upon sensing the second status change; 
 means for determining a number of tap step changes of the load tap changer drive from the first and second data readings; and 
 means for determining a new load tap changer position based on the number of tap step changes. 
 
   
   
     29. A system for remotely tracking load tap position changes at a power transformer, the system comprising:
 means for determining a starting position of a load tap changer of the power transformer; 
 means for measuring an elapsed time between a first status change in a load tap changer circuit arrangement and a second status change in the load tap changer circuit arrangement; 
 means for determining a number of tap step changes of the load tap changer based upon the elapsed time; and 
 means for determining a new load tap changer position. 
 
   
   
     30. A method for remotely tracking load tap position changes at a power transformer, the method comprising:
 determining a starting position of a load tap changer of the power transformer; 
 initiating a timer and initiating a first data reading upon sensing without using a physical position encoder a first status change in a load tap changer circuit arrangement; 
 stopping the timer and initiating a second data reading upon sensing without using a physical position encoder a second status change in the load tap changer circuit arrangement; 
 determining a number of tap step changes of the load tap changer from an elapsed time measured by the timer and from the first and second data readings; and 
 determining a new load tap changer position.